LONDON (Reuters) - The fitness of Olympic badminton silver medallist Lee Chong Wei is a state "secret" that cannot be revealed before the London Games tournament, according to Malaysia's chef de mission.

Lee Chong Wei of Malaysia returns a shot against Shon Wan-Ho of South Korea during their men's single final match at the India Open Super Series badminton tournament in New Delhi April 29, 2012. REUTERS/Adnan Abidi

The top seed Lee, Malaysia's brightest hope of a maiden Olympic gold medal, has been battling to get back to peak form for the July 28-August 5 tournament at Wembley Arena since injuring an ankle during a Thomas Cup match in May.

"He is here. I cannot tell you about his form, but he is here," Malaysia chef de mission Tun Ahmad Sarji told Reuters at Olympic Park.

"I think his (fitness) is a Malaysian secret ... Every country should keep their own secrets, right?" Malaysia's badminton teams have won all of the country's medals since the sport joined the Olympic programme in 1992 and former world number one Lee reached the final at Beijing but was trounced by China's Lin Dan.

Lee said his ankle was "70 percent" when briefing reporters a month before the Games and faces an uphill battle to be fit for the opening round on Saturday at the Wembley Arena.

Lee, who will compete in his last Games at London, faces Finland's Ville Lang in the first round before a potential round of 16 match against Indonesia's world number six Simon Santoso. (Editing by Greg Stutchbury)